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Michelle R. Butler, Patricia Chevez-Barrios, Benjamin J. Frankfort; The Evaluation of Silver Nanoparticles as an Adjunct to Trabeculectomy in Rabbits. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2523.
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To assess whether the topical application of silver nanoparticles modifies the healing response following trabeculectomy surgery in rabbits.
Six Dutch Belt Pigmented female rabbits underwent trabeculectomy surgery performed by a single surgeon (BJF). Animals were randomized 1:1 to two treatment groups in which the adjuvant was applied with soaked sponges to the subconjunctival space: 1) a 2 minute application of Mitomycin C (MMC, 0.4mg/mL) which was repeated and then irrigated; or 2) a 4 minute application of silver nanoparticles (10 nm average diameter, 0.1 mg/mL colloidal solution in water, Plasmachem, Berlin, Germany) without irrigation. A 22 gauge intravenous catheter was inserted into the anterior chamber through a 3mm scleral tunnel to ensure patency of the sclerostomy. The rabbits were evaluated on post-operative day 1 and weeks 1-6. At all time points, recordings were made of intraocular pressure (IOP) with a tonopen, bleb characteristics (thickness, height, width), vascularity, anterior chamber depth, and complications. The operative eyes were enucleated at post-operative week six and analyzed histologically and by immunohistochemistry.
The average pre-operative IOP of the MMC- and silver-treated eyes was 20.1 and 19.8 mmHg, respectively. The IOP at week six was lower in all rabbits, with an average decrease of 6.0 mmHg (MMC) or 7.1 mmHg (silver). Bleb thickness (0= thin, 1=intermediate, 2=thick) averaged between thin and intermediate prior to enucleation in both groups. Average bleb dimensions were 0.67 x 1.50mm (MMC) and 1.33 x 2.00mm (silver). For both groups, bleb vascularity (0=minimal, 1=intermediate, 2=significant) averaged between minimal and intermediate. The anterior chamber remained deep in all rabbits. There were no bleb leaks. One MMC-treated rabbit developed an infection and was treated with topical antibiotics, but the bleb subsequently failed. A second MMC-treated rabbit had probable bleb failure, while no silver-treated rabbits had clinical evidence of bleb failure. On histologic exam, both groups had chronic inflammation, but there was reduced fibrosis and no myofibroblasts in the silver-treated eyes. The MMC treated eyes had prominent smooth muscle actin positive myofibroblasts in the fibrous tissue around the empty space of the bleb. There was a mild eosinophilic infiltrate present in silver-treated eyes.
The application of silver nanoparticles as an adjuvant to trabeculectomy surgery in rabbits does not appear to be inferior to MMC and may reduce the complications and post-operative fibrosis. This may be due to the absence of myofibroblasts resulting in a lack of contraction of the fibrous tissue. Further study is warranted.
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